Lawn mower

ABSTRACT

A lawn mower includes: a mower unit having a plurality of blades for performing lawn mowing work, the plurality of blades being driven by rotational power, a blade motor configured to transmit rotational power to each of the plurality of blades, and be capable of optionally changing the rotation number of the rotational power transmitted to each of the plurality of blades; and a controller configured to detect respective speeds of the plurality of blades to the ground and perform energy-saving control of increasing and decreasing the rotation number of the rotational power transmitted to each of the plurality of blades in accordance with increase and reduction in the detected speed of each of the plurality of blades.

CROSS-REFERENCE TO RELATED APPLICATIONS

The instant application is a Continuation of U.S. non-provisionalapplication Ser. No. 14/483,416 filed on Sep. 11, 2014, whichapplication claims priority under 35 U.S.C. §119 of Japanese ApplicationNo. 2014-008152, filed on Jan. 20, 2014. The disclosure of eachapplication is herein expressly incorporated by reference in itsentirety.

TECHNICAL FIELD

The disclosure relates to a technology of a lawn mower including a workdevice having a plurality of blades for performing lawn mowing work.

BACKGROUND ART

Heretofore, there is publicly known a technology of a lawn mowerincluding a work device having a plurality of blades for performing lawnmowing work, for example, as disclosed in JP 2013-253510 A.

JP 2013-253510 A discloses a lawn mower including a mower unit thatserves as a work device. The mower unit has a plurality of blades. In acase where it is detected that power from an engine is transmitted tothe mower unit, the lawn mower can control the engine by isochronouscontrol.

Thus, in a case where power is transmitted to the mower unit, it isdetermined that the mower unit is in the course of lawn mowing work, andthe engine is controlled by isochronous control. Consequently, even whena load applied to the engine is fluctuated, an engine rotational speedcan be maintained constant, and the rotation numbers of the plurality ofblades can be also maintained constant.

However, in the lawn mower disclosed in JP 2013-253510 A, the pluralityof blades are driven through a single belt (belt transmissionmechanism), and therefore the plurality of blades rotate at the samerotation number. Accordingly, the lawn mower has room for improvement inenergy saving performance. Hereinafter, specific description is made.

Generally, the plurality of blades are disposed side by side in a leftand right direction. Therefore, when the lawn mower turns left andright, the speeds of the plurality of blades to the ground are differentfrom each other. Specifically, the speed of a blade disposed on an innerside in a turning direction (hereinafter, simply described as an “innerblade”) is smaller (slower) than the speed of a blade disposed on anouter side in the turning direction (hereinafter, simply described as an“outer blade”). In this case, even when the rotation number of the innerblade is made smaller than the rotation number of the outer blade, it ispossible to perform work (lawn mowing work) with respect to the groundwith accuracy equal to the outer blade. Therefore, a conventionaltechnology of rotating a plurality of blades at the same rotation numberincludes inefficient work and has room for improvement in energy savingperformance.

SUMMARY OF INVENTION

In view of the above circumstances, an object of the disclosure is toprovide a lawn mower capable of improving energy saving performance.

The problem to be solved by the disclosure has been described above, andmeans for solving the problem is now described.

That is, a lawn mower according to the disclosure includes: a workdevice having a plurality of blades for performing lawn mowing work, theplurality of blades being driven by rotational power, a power deviceconfigured to transmit rotational power to each of the plurality ofblades, and be capable of optionally changing the rotation number of therotational power transmitted to each of the plurality of blades; a bladespeed detection unit configured to detect respective speeds of theplurality of blades to a ground; and a control device configured toperform energy-saving control of increasing and decreasing the rotationnumber of the rotational power transmitted to each of the plurality ofblades in accordance with increase and reduction in the detected speedof each of the plurality of blades.

As effects of the disclosure, the following effects are obtained.

In the lawn mower according to the disclosure, the rotation number ofthe rotational power transmitted to each of the blades is increased anddecreased in accordance with increase and reduction in the speed of eachof the plurality of blades to the ground, so that excessive rotationalpower can be prevented from being transmitted to the blades, and energysaving performance can be improved. Particularly, in a case where thespeeds of the respective blades are different, the rotation number ofthe rotational power transmitted to each of the blades can beindividually increased and decreased, and energy saving performance canbe effectively improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a situation where a worker rides on a lawnmower according to an embodiment of the disclosure;

FIG. 2 is side view of the lawn mower of this embodiment;

FIG. 3 is a rear view of the lawn mower;

FIG. 4 is a back perspective view of the lawn mower;

FIG. 5 is a plan view of the lawn mower;

FIG. 6 is a side view showing a traveling machine body and a ridingpart;

FIG. 7 is a rear view showing the traveling machine body and the ridingpart;

FIG. 8 is an exploded perspective view showing the riding part;

FIG. 9 is a plan view of the riding part;

FIG. 10 is a schematic diagram showing a configuration related to thecontrol of the lawn mower;

FIG. 11 is a schematic plan view showing various elements of the lawnmower.

FIG. 12 is a flowchart showing the contents of energy-saving control;

FIG. 13 is a diagram showing a rotation number map;

FIG. 14 is a diagram showing an electric power consumption thresholdmap;

FIG. 15 is a schematic plan view showing a situation of lawn mowing workby the lawn mower;

FIG. 16 is a schematic plan view showing a difference between the speedsof blades when the lawn mower is turned; and

FIGS. 17A, 17B and 17C are diagrams showing other examples of therotation number map.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the direction of an arrow U, the direction of an arrow D,the direction of an arrow L, the direction of an arrow R, the directionof an arrow F, and the direction of an arrow B shown in the drawings aredefined as an upper direction, a lower direction, a left direction, aright direction, a front direction, and a back direction, respectively,and description is made.

Hereinafter, an entire configuration of a lawn mower 1 according to anembodiment (first embodiment) of the disclosure is described withreference to FIG. 1 to FIG. 5.

The lawn mower 1, on which a worker rides, travels, and enables theworker to perform predetermined work to the ground (lawn mowing work).The lawn mower 1 mainly includes a traveling machine body 10, a motivepower part 20, a driving wheel 30L and a driving wheel 30R, a ridingpart 40, a driven wheel 60L and a driven wheel 60R, a handle 70, and amower unit 90.

The traveling machine body 10 is supported by a pair of the left andright driving wheels 30L and 30R. The traveling machine body 10 isprovided with the motive power part 20 for driving the pair of left andright driving wheels 30L and 30R. To the back part of the travelingmachine body 10, the riding part 40 on which the worker rides isconnected. In both the left and right ends of the riding part 40, thedriven wheel 60L and the driven wheel 60R are provided respectively. Tothe upper part of the traveling machine body 10, the handle 70 isconnected, and is provided so as to extend upward. To the front part ofthe traveling machine body 10, the mower unit 90 that is a work devicefor grass mowing (particularly, lawn mowing) is connected.

In the lawn mower 1 thus configured, the worker rides on the riding part40 to grip the handle 70 by a hand, so that the worker can stably rideon the lawn mower 1. Additionally, the worker performs predeterminedoperation, so that the worker can independently drive the pair of leftand right driving wheels 30L and 30R to enable the lawn mower 1 totravel arbitrarily. That is, while arbitrarily steering the lawn mower 1left and right, the worker can move the lawn mower 1 forward orbackward, and turn the lawn mower 1 on the spot. Furthermore, the workerperforms predetermined operation, so that the worker drives the mowerunit 90 to enable lawn mowing work.

Hereinafter, a configuration of each part of the lawn mower 1 isdescribed.

The traveling machine body 10 shown in FIG. 1 to FIG. 7 mainly includesa machine body frame 11, and a machine body cover 12.

The machine body frame 11 shown in FIG. 4 to FIG. 7 serves as a mainstructure of the traveling machine body 10. The machine body frame 11 isformed by combining a plurality of cylindrical members which areproperly bent, or plate-shaped members. A space surrounded by themachine body frame 11 is a housing space S for housing component membersof the motive power part 20 described later.

The machine body cover 12 shown in FIG. 1 and FIG. 2 is fixed to themachine body frame 11 so as to cover the housing space S of the machinebody frame 11. The machine body cover 12 can conceals the machine bodyframe 11 or a device provided in the machine body frame 11 (motive powerpart 20 described later).

The motive power part 20 shown in FIG. 4 to FIG. 7 generates power fordriving the driving wheel 30L and the driving wheel 30R, and transmitsthe power to the driving wheel 30L and the driving wheel 30R. The motivepower part 20 mainly includes a battery 21, a left motor 22L and a rightmotor 22R, a left power transmission mechanism 23L and a right powertransmission mechanism 23R, and a controller box 24.

The battery 21 stores electric power for driving the lawn mower 1. Thebattery 21 is disposed in the lower part of the housing space S so as torange from the front end to the rear end of the housing space S.

The left motor 22L and the right motor 22R are power sources forindependently driving the pair of left and right driving wheels 30L and30R, respectively. The left motor 22L and the right motor 22R cangenerate rotational power by using supplied electric power. The leftmotor 22L and the right motor 22R are disposed side by side in the leftand right direction inside the housing space S, respectively. The leftmotor 22L and the right motor 22R are disposed on substantially thecentral part in the front and back direction of the housing space Sright above the battery 21.

The left power transmission mechanism 23L and the right powertransmission mechanism 23R properly decelerate power from the left motor22L and the right motor 22R, and thereafter transmit the deceleratedpower to the pair of left and right driving wheels 30L and 30R. The leftpower transmission mechanism 23L is connected to the left motor 22L tobe fixed to the left side surface of the machine body frame 11. Theright power transmission mechanism 23R is connected to the right motor22R to be fixed to the right side surface of the machine body frame 11.The left power transmission mechanism 23L has an axle (output shaft)that is connected to the driving wheel 30L, and the right powertransmission mechanism 23R has an axle that is connected to the drivingwheel 30R. The axle of the left power transmission mechanism 23L and theaxle of the right power transmission mechanism 23R are disposed on thesame axis, and therefore the pair of left and right driving wheels 30Land 30R are disposed on the same axis.

The controller box 24 houses devices for controlling the driving of thelawn mower 1 (specifically, a controller 24 a, a left inverter 24 b, aright inverter 24 c, a left working inverter 24 d, a right workinginverter 24 e, and the like which are described later). The controllerbox 24 is disposed in the upper part of the housing space S so as torange from the front to the back of the left motor 22L and the rightmotor 22R through the upper parts.

The controller 24 a and the like housed in the controller box 24 aredescribed later.

The driving wheel 30L and the driving wheel 30R support the travelingmachine body 10, and rotate to allow the traveling machine body 10 totravel. The driving wheel 30L and the driving wheel 30R support thetraveling machine body 10 through the motive power part 20 (the leftpower transmission mechanism 23L and the right power transmissionmechanism 23R).

The riding part 40 shown in FIG. 6 to FIG. 9 is disposed behind thetraveling machine body 10, is connected to the traveling machine body10, and is configured to enable the riding of the worker. The ridingpart 40 mainly includes a first member 41 and a second member 43.

The first member 41 is a plate-shaped member. The first member 41 mainlyincludes a central part 41 a, a left part 41 b, and a right part 41 c.

The central part 41 a is a part formed in a rectangle in plan view. Theleft part 41 b and the right part 41 c are parts formed by bending theleft end and the right end of the first member 41 such that the left endand the right end rise. The bottom surface of the central part 41 a isconnected to the rear end of the machine body frame 11.

The second member 43 is a plate-shaped member. The second member 43 isformed in a rectangle that is one size smaller than the central part 41a of the first member 41, in plan view. In the central part in the leftand right direction of the second member 43, a partition part 43 a isformed. The partition part 43 a is a part formed such that the centralpart in the left and right direction of the second member 43 rises fromthe front to the back. In the front end of the partition part 43 a, anopening 43 b that communicates the inside and the outside of thepartition part 43 a is formed. The partition part 43 a partitions theupper surface of the second member 43 into the left and the right.

The surface on the left of the thus partitioned upper surface of thesecond member 43 serves as a left leg placing surface 44L for placing aleft leg of the worker. Similarly, the surface on the right of the uppersurface of the second member 43 serves as a right leg placing surface44R for placing a right leg of the worker. The partition part 43 a isformed in the second member 43, so that a part where the left leg of theworker is placed, and a part where the right leg is placed can beapparently distinguished. The second member 43 is disposed on the upperpart of the central part 41 a of the first member 41.

Between the first member 41 and the second member 43, a plurality ofload sensors (a left front load sensor 50 a, a left back load sensor 50b, a right front load sensor 50 c, and a right back load sensor 50 d)are disposed. Specifically, the second member 43 is placed on theplurality of load sensors disposed on the upper surface of the firstmember 41. The plurality of load sensors can detect a load applied tothe second member 43 (specifically, a load by the worker who riding onthe second member 43).

The left front load sensor 50 a is disposed near the front end of theleft leg placing surface 44L of the second member 43 in plan view.

The left back load sensor 50 b is disposed behind the left front loadsensor 50 a and near the rear end of the left leg placing surface 44L ofthe second member 43 in plan view.

The right front load sensor 50 c is disposed near the front end of theright leg placing surface 44R of the second member 43 (at a positionsymmetrical to the left front load sensor 50 a with the partition part43 a interposed between the right front load sensor 50 c and the leftfront load sensor 50 a) in plan view.

The right back load sensor 50 d is disposed near the rear end of theright leg placing surface 44R of the second member 43 (at a positionsymmetrical to the left back load sensor 50 b with the partition part 43a interposed between the right back load sensor 50 d and the left backload sensor 50 b) in plan view.

Thus, the left front load sensor 50 a and the right front load sensor 50c, and the left back load sensor 50 b and the right back load sensor 50d are disposed by being shifted in the front and back direction.Additionally, the left front load sensor 50 a and the left back loadsensor 50 b, and the right front load sensor 50 c and the right backload sensor 50 d are disposed by being shifted in the left and rightdirection.

Wires 51 connected to the left front load sensor 50 a, the left backload sensor 50 b, the right front load sensor 50 c, and the right backload sensor 50 d are collected to the center in the left and rightdirection, and are guided forward through a space inside the partitionpart 43 a of the second member 43. The wires 51 are guided to theoutside of the partition part 43 a through the opening 43 b, to beconnected to the controller 24 a described later.

The driven wheel 60L and the driven wheel 60R support the riding part.The driven wheel 60L and the driven wheel 60R are provided below theleft part 41 b and the right part 41 c of the first member 41,respectively. The driven wheel 60L and the driven wheel 60R arenon-driving wheels, and can rotate while freely changing the directionin accordance with the movement of the lawn mower 1.

The handle 70 shown in FIG. 2 to FIG. 7 is connected to the travelingmachine body 10 so as to be swingable left and right with respect to thetraveling machine body 10. The handle 70 mainly includes a fulcrum shaft71, a handle main body 72, a grip part 73, a work switch 74, and acontrol changeover switch 75.

The fulcrum shaft 71 shown in FIG. 6 and FIG. 7 serves as a swingfulcrum of the handle 70. The fulcrum shaft 71 is rotatably supported bythe upper end of the machine body frame 11 with the longitudinaldirection of the fulcrum shaft 71 being directed in the front and backdirection.

The handle main body 72 shown in FIG. 2 to FIG. 4 serves as a mainstructure of the handle 70. The handle main body 72 is provided so as toextend upward from the rear upper part of the traveling machine body 10.The lower end of the handle main body 72 is fixed to the rear end of thefulcrum shaft 71. Consequently, the handle main body 72 is connected tothe traveling machine body 10 so as to be swingable left and right withrespect to the traveling machine body 10.

The grip part 73 shown in FIG. 2 to FIG. 4 is a part where the workerwho is riding on the riding part 40 can grip by a hand. The grip part 73is formed so as to extend from the upper end of the handle main body 72to the left and right. The height of the grip part 73 (i.e., the heightof the upper end of the handle main body 72) is preset to a heightallowing easy gripping of the worker who is riding on the riding part 40(e.g., a height equal to the level of a chest of the worker (see FIG.1)).

The work switch 74 is an operation tool for switching on and off of thedriving of the mower unit 90 described later. The work switch 74 isprovided in the middle in the vertical direction of the handle main body72.

The control changeover switch 75 is an embodiment of a selection unitaccording to the disclosure, and is an operation tool for switchingcontrol performed by the controller 24 a described later. The controlchangeover switch 75 is provided in the middle in the vertical directionof the handle main body 72.

In the handle 70 thus configured, the worker can grip the grip part 73and swingably operate the handle main body 72 (handle 70) left and rightwith the fulcrum shaft 71 as a swing fulcrum.

As shown in FIG. 6, to the front end of the fulcrum shaft 71, a rotationangle sensor 80 is connected. The rotation angle sensor 80 is configuredby a potentiometer. The rotation angle sensor 80 is fixed to the upperend of the machine body frame 11, and is connected to the front end ofthe fulcrum shaft 71. Consequently, the rotation angle sensor 80 candetect the rotation angle of the fulcrum shaft 71, and also detect theswinging operation amount of the handle 70.

The mower unit 90 shown in FIG. 4 to FIG. 6 is an embodiment of a workdevice according to the disclosure, and is a work device for performinglawn mowing work. The mower unit 90 mainly includes a mower deck 95,blades 91, blade motors 92, a gauge wheel 93, and a lifting and loweringlink 94.

The mower deck 95 serves as a main structure of the mower unit 90. Themower deck 95 is formed in a substantially box shape with an openedbottom surface. In the right end of the mower deck 95, a discharge port95 a (see FIG. 5) for communicating the inside and the outside of themower deck 95 is formed. The discharge port 95 a is covered by a guidemember 95 b from the above.

The blades 91 are tools for mowing lawn (performing lawn mowing work),driven by rotational power. The two blades 91 are disposed side by sidein the substantially left and right direction inside the mower deck 95.Hereinafter, the blade 91 disposed on the left side is described as aleft blade 91L, and the blade 91 disposed on the right side is describedas a right blade 91R.

The blade motors 92 are an embodiment of a power device and a workingmotor according to the disclosure, and generate rotational power forrotating the blades 91 by using electric power. The blade motors 92 areprovided to correspond to the respective two blades 91. The blade motors92 are provided on the upper part of the mower deck 95. The outputshafts of the blade motors 92 are provided so as to extend downward (inthe mower deck 95), and connected to the respective blades 91. Therespective rotation numbers of the two blade motors 92 can be optionallychanged. Hereinafter, the blade motor 92 provided to correspond to theleft blade 91L is described as a left blade motor 92L, and the blademotor 92 provided to correspond to the right blade 91R is described as aright blade motor 92R.

The gauge wheel 93 supports the mower deck 95. The gauge wheel 93 isprovided in the front end of the mower deck 95. The gauge wheel 93 is anon-driving wheel, and can rotate while freely changing the direction inaccordance with the movement of the lawn mower 1.

The lifting and lowering link 94 is a link for liftably connecting themower deck 95 to the traveling machine body 10. The lifting and loweringlink 94 has a first end (front end) connected to the rear end of themower deck 95. The lifting and lowering link 94 has a second end (rearend) connected to the front end of the machine body frame 11 of thetraveling machine body 10. The lifting and lowering link 94 includes anelectric cylinder 94 a. The electric cylinder 94 a is extended andcontracted, so that the mower deck 95 can be lifted and lowered withrespect to the traveling machine body 10.

Hereinafter, a configuration for controlling the driving of the lawnmower 1 is described with reference to FIG. 10.

The controller 24 a is an embodiment of a control device, a firstcalculation unit, and a second calculation unit according to thedisclosure, and controls the operation of each connected device. Thecontroller 24 a is configured by a storage part, an arithmeticprocessing part, and the like. The controller 24 a stores a program forcontrolling each device and various data.

The controller 24 a is connected to the left front load sensor 50 a, theleft back load sensor 50 b, the right front load sensor 50 c, and theright back load sensor 50 d, and can receive results of loads detectedby these load sensors.

The controller 24 a is connected to the rotation angle sensor 80, andcan receive a result of the swinging operation amount of the handle 70detected by the rotation angle sensor 80.

The controller 24 a is connected to the work switch 74, and can receivea signal related to the operation of the work switch 74.

The controller 24 a is connected to the control changeover switch 75,and can receive a signal related to the operation of the controlchangeover switch 75.

The controller 24 a is connected to the left inverter 24 b, and cancontrol the driving of the left inverter 24 b. The controller 24 aoptionally supplies electric power from the battery 21 to the left motor22L through the left inverter 24 b, so that the rotational speed of thedriving wheel 30L can be optionally controlled.

The controller 24 a is connected to the right inverter 24 c, and cancontrol the driving of the right inverter 24 c. The controller 24 aoptionally supplies electric power from the battery 21 to the rightmotor 22R through the right inverter 24 c, so that the rotational speedof the driving wheel 30R can be optionally controlled.

The controller 24 a is connected to the left working inverter 24 d, andcan control the driving of the left working inverter 24 d. Thecontroller 24 a optionally supplies electric power from the battery 21to the left blade motor 92L through the left working inverter 24 d, sothat the rotational speed of the left blade 91L can be optionallycontrolled, and perform lawn mowing work. Additionally, the controller24 a can detect electric power (electric power consumption) consumed bythe left blade motor 92L, through the left working inverter 24 d.

The controller 24 a is connected to the right working inverter 24 e, andcan control the driving of the right working inverter 24 e. Thecontroller 24 a optionally supplies electric power from the battery 21to the right blade motor 92R through the right working inverter 24 e, sothat the rotational speed of the right blade 91R can be optionallycontrolled, and perform lawn mowing work. Additionally, the controller24 a can detect electric power consumption of the right blade motor 92Rthrough the right working inverter 24 e.

The controller 24 a is connected to the electric cylinder 94 a of thelifting and lowering link 94, and can change the length of the electriccylinder 94 a. When a mower height adjusting switch (not shown) providedin the handle 70 is operated, the controller 24 a can change the lengthof the electric cylinder 94 a in accordance with the operation amount ofthe mower height adjusting switch, and also change the height of themower deck 95.

Hereinafter, description is given of control performed by controller 24a when a worker drives the lawn mower 1 configured as described above.

First, control performed by the controller 24 a when the lawn mower 1 isallowed to travel (is moved forward or backward) is described.

In a case where the lawn mower 1 is driven, the worker rides on theriding part 40, and grips the grip part 73 of the handle 70 by a hand(see FIG. 1). At this time, a left leg and a right leg of the worker areplaced on the left leg placing surface 44L and the right leg placingsurface 44R, respectively (see FIG. 9).

When the worker shifts his/her weight forward and backward(specifically, applies his/her weight to toes or heels), the controller24 a moves the lawn mower 1 forward or backward based on the forward andbackward weight shift of the worker. Hereinafter, specific descriptionis made.

The controller 24 a calculates a forward and backward weight shift ofthe worker based on loads always detected by the plurality of loadsensors (the left front load sensor 50 a, the left back load sensor 50b, the right front load sensor 50 c, and the right back load sensor 50d). Specifically, the controller 24 a calculates a weight shift of theworker from change of balance between a total value of loads detected bythe left front load sensor 50 a and the right front load sensor 50 c,and a total value of loads detected by the left back load sensor 50 b,and the right back load sensor 50 d.

The detection values of the plurality of load sensors that are used as areference of the calculation of the weight shift (detection valuesdetected when the traveling vehicle neither move forward nor backward)can be set by an arbitrary method. For example, the controller 24 a canbe configured to previously store the detection values, or storedetection values of the plurality of load sensors detected when theworker rides on the riding part 40.

In a case where the controller 24 a determines that the weight shift ofthe worker occurs, the controller 24 a supplies electric power to theleft motor 22L and the right motor 22R to drive the driving wheel 30Land the driving wheel 30R. Specifically, in a case where a forwardweight shift occurs, the controller 24 a rotates the driving wheel 30Land the driving wheel 30R forward to move the lawn mower 1 forward. In acase where a backward weight shift occurs, the controller 24 a rotatesthe driving wheel 30L and the driving wheel 30R backward to move thelawn mower 1 backward. Additionally, the controller 24 a increases therotational speeds of the driving wheel 30L and the driving wheel 30R asthe weight shift amount of the worker is larger, and moves the lawnmower 1 forward or backward at a higher speed.

When the worker swings the handle 70 left and right, the controller 24 aturns the lawn mower 1 left or right based on the swinging operationamount of the handle 70. Hereinafter, specific description is made.

The controller 24 a supplies electric power to the left motor 22L andthe right motor 22R based on the swinging operation amount of the handle70 always detected by the rotation angle sensor 80, to drive the drivingwheel 30L and the driving wheel 30R. Specifically, when the handle 70 isswingably operated left, the controller 24 a rotates the driving wheel30L backward, and rotates the driving wheel 30R forward, to turn thelawn mower 1 in the left direction on the spot. Additionally, when thehandle 70 is swingably operated right, the controller 24 a rotates thedriving wheel 30L forward, and rotates the driving wheel 30R backward,to turn the lawn mower 1 in the right direction on the spot.

Furthermore, when the weight shift of the worker and the swingingoperation of the handle 70 are performed at the same time, thecontroller 24 a can turn the lawn mower 1 left or right while moving thelawn mower 1 forward or backward (i.e., turn to the left or the right).Thus, the worker performs the weight shift and the swinging operation ofthe handle 70, so that the worker can intuitively drive the lawn mower1.

Control performed by the controller 24 a when lawn mowing work isperformed by using the mower unit 90 of the lawn mower 1 is nowdescribed.

When the worker operates the work switch 74 (ON operation), thecontroller 24 a supplies electric power to the blade motors 92 to rotatethe blades 91. The lawn mower 1 is allowed to travel in this state, sothat lawn mowing work can be performed. Furthermore, when the workeroperates the work switch 74 (OFF operation), the controller 24 a stopssupplying electric power to the blade motors 92, to stop rotating theblades 91.

As a method of controlling the rotation numbers of the blades 91, thecontroller 24 a can select any one of non-energy-saving control andenergy-saving control to perform the control.

The non-energy-saving control is control for keeping the rotationnumbers of the two blades 91 constant. Specifically, in a case where thenon-energy-saving control is selected, the controller 24 a alwaysrotates the two blades 91 (the left blade 91L and the right blade 91R)at the maximum rotation number. In the non-energy-saving control, therotation numbers of the blades 91 are never changed (particularly,decreased). Therefore, in a case where work of blowing and dischargingmown lawns, dead leaves or the like from the discharge port 95 a byutilizing wind generated by the rotation of the blades 91 is performed,the non-energy-saving control is more suitable than the energy-savingcontrol described later.

The rotation numbers of the blades 91 in the non-energy-saving controlare not limited to the maximum rotation number, and can be preset to anarbitrary value.

The energy-saving control is control of increasing and decreasing therespective rotation numbers of the two blades 91 in accordance withincrease and reduction of the speeds of the two blades 91 to the ground.Specifically, the controller 24 a previously stores a rotation numbermap (see FIG. 13. Details are described later) showing a relationbetween the speeds of the blades 91 to the ground, and the rotationnumbers of the blades 91 (blade motors 92) suitable for the speeds. Therotation number map is set so as to decrease the rotation numbers of theblades 91 as the speeds of the blades 91 to the ground reduce. In a casewhere the energy-saving control is selected, the controller 24 aincreases and decreases the respective rotation numbers of the twoblades 91 in accordance with increase and reduction of the speeds of thetwo blades 91 to the ground, based on the rotation number map.

The controller 24 a performs such energy-saving control, so that therotation numbers of the blades 91 can be decreased to reduce electricpower consumed in order to rotate the blades 91, in a case where thespeeds of the blades 91 to the ground reduce.

The detailed contents of the energy-saving control are described later.

Each time the worker operates the control changeover switch 75, thecontroller 24 a switches between the above non-energy-saving control andenergy-saving control. That is, by simply operating the controlchangeover switch 75, the worker can optionally select thenon-energy-saving control or the energy-saving control to perform thecontrol.

Hereinafter, the details of the energy-saving control performed by thecontroller 24 a is described. In a case where the worker operates theenergy-saving control, the controller 24 a sequentially performsprocesses shown in FIG. 12.

Herein, when processes in step S101 and step S102 in FIG. 12, describedlater are performed, various elements (dimensions) of the lawn mower 1are used. Specifically, as shown in FIG. 11, a distance (tread) XDbetween the centers of the left and right driving wheels (the drivingwheel 30L and the driving wheel 30R), a distance XL in the left andright direction from the intermediate point G of the left and rightdriving wheels to the center of the left blade 91L, a distance XR in theleft and right direction from the intermediate point G to the center ofright blade 91R, a distance YL in the front and back direction from theintermediate point G to the center of the left blade 91L, and a distanceYR in the front and back direction from the intermediate point G to thecenter of the right blade 91R are used.

The above distance XD, distance XL and distance XR each are a fixedvalue (value determined by a configuration of the lawn mower 1), andpreviously stored in the controller 24 a.

The above distance YL and distance YR change in accordance with theheight of the mower deck 95 (i.e., length of the electric cylinder 94 a)lifted and lowered by the lifting and lowering link 94. The controller24 a previously stores a map showing relations between the length of theelectric cylinder 94 a and the distances YL and YR. The controller 24 acan calculate the distance YL and the distance YR based on the length ofthe electric cylinder 94 a and the map.

In a flowchart shown in FIG. 12, the left blade 91L (left blade motor92L) and the right blade 91R (right blade motor 92R) are controlled in asimilar manner. Accordingly, the following description is made whilemainly focusing on the left blade 91L (left blade motor 92L), anddescription for the right blade 91R (right blade motor 92R) is added asnecessary.

In step S101 of FIG. 12, the controller 24 a detects the speed V and theangular speed co of the traveling machine body 10 to the ground (morespecifically, at the intermediate point G). Specifically, the controller24 a first calculates (detects) the speed VL of the driving wheel 30L tothe ground and the speed VR of the driving wheel 30R to the ground byusing the following Expression 1 and Expression 2.

VL=Y0L×N×π×D  [Expression 1]

VR=V0R×N×π×D  [Expression 2]

Herein, V0L, V0R, N, and D in the above Expression 1 and Expression 2denote the rotation number of the left motor 22L per unit time, therotation number of the right motor 22R per unit time, the reductionratio of each of the left power transmission mechanism 23L and the rightpower transmission mechanism 23R, and the diameter of each of thedriving wheel 30L and the driving wheel 30R, respectively.

Thus, the left motor 22L, the right motor 22R, and the controller 24 aconfigure a unit for detecting the speed VL of the driving wheel 30L andthe speed VR of the driving wheel 30R (driving wheel speed detectionunit according to the disclosure).

Now, the controller 24 a calculates (detects) the speed V of thetraveling machine body 10 by using the following Expression 3.

V=(L+VR)/2  [Expression 3]

The controller 24 a calculates the angular speed ω of the travelingmachine body 10 by using the following Expression 4.

ω=(VL−VR)/XD  [Expression 4]

Thus, the above driving wheel speed detection unit and the controller 24a configure a unit for detecting the speed V and the angular speed ω ofthe traveling machine body 10 (machine body speed detection unitaccording to the disclosure).

The controller 24 a advances to step S102 after performing the processin step S101.

In step S102, the controller 24 a detects the speed VBL of the leftblade 91L to the ground (more specifically, of the center of the leftblade 91L). Specifically, the controller 24 a first calculates adistance RL from the intermediate point G to the center of the leftblade 91L in plan view (see FIG. 11) by using the following Expression5.

RL=√{square root over (XL ² +YL ²)}  [Expression 5]

Then, the controller 24 a calculates (detects) the speed VBL of the leftblade 91L to the ground by using the following Expression 6.

$\begin{matrix}\begin{matrix}{{VBL} = {V + {{RL} \times {\omega }}}} \\{= {{\left( {{VL} + {VR}} \right)/2} + {\sqrt{{XL}^{2} + {YL}^{2}} \times}}} \\{{{{{VL} - {VR}}}/{XD}}}\end{matrix} & \left\lbrack {{Expression}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In a case where the speed VBR of the right blade 91R (more specifically,of the center of the right blade 91R) is detected, the controller 24 afirst calculates a distance RR from the intermediate point G to thecenter of the right blade 91R in plan view (see FIG. 11) by using thefollowing Expression 7.

RR=√{square root over (XR ² +YR ²)}  [Expression 7]

Then, the controller 24 a calculates (detects) the speed VBR of theright blade 91R to the ground by using the following Expression 8.

$\begin{matrix}\begin{matrix}{{VBR} = {V + {{RR} \times {\omega }}}} \\{= {{\left( {{VL} + {VR}} \right)/2} + {\sqrt{{XR}^{2} + {YR}^{2}} \times}}} \\{{{{{VL} - {VR}}}/{XD}}}\end{matrix} & \left\lbrack {{Expression}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Thus, the above machine body speed detection unit and the controller 24a configure a unit for detecting the speed VBL of the left blade 91L andthe speed VBR of the right blade 91R (blade speed detection unitaccording to the disclosure).

The controller 24 a advances to step S103 after performing the processin step S102.

In step S103, the controller 24 a determines a target value of therotation number of the left blade 91L, namely a target value VML of therotation number (the target rotation number) of the left blade motor92L. Specifically, the controller 24 a determines the target rotationnumber VML of the left blade motor 92L based on the previously storedrotation number map (see FIG. 13), and the speed VBL of the left blade91L to the ground, which is detected in step S102.

Herein, the above rotation number map is described with reference toFIG. 13.

The rotation number map shows relations between the speeds of the blades91 (the speed VBL of the left blade 91L and the speed VBR of the rightblade 91R), and the target rotation numbers of the blade motors 92 (thetarget rotation number VML of the left blade motor 92L and the targetrotation number VMR of the right blade motor 92R) suitable for lawnmowing work performed by the blades 91 moving at the speeds. Therotation number map is preset based on experimentation, a numericalanalysis, or the like.

In the rotation number map, a relation between the speed VBL and thetarget rotation number VML, and a relation between the speed VBR and thetarget rotation number VMR are set to be the same. Accordingly, therotation number map is hereinafter described by focusing on the relationbetween the speed VBL and the target rotation number VML.

In the rotation number map, in a case where the speed VBL of the leftblade 91L is 0, the target rotation number VML of the left blade motor92L is set to VM0.

Additionally, in the rotation number map, in a case where the speed VBLof the left blade 91L is within a range from greater than 0 to notgreater than VB1 (0<VBL≦VB1), the target rotation number VML of the leftblade motor 92L is set to VM1 (a value greater than VM0). The value VM1of this target rotation number VML is set to the minimum rotation numberrequired for performing lawn mowing work by the blades 91.

Herein, as the speed VBL of the left blade 91L increases, an area wherethe left blade 91L performs lawn mowing work per unit time increases.Therefore, in order to suitably perform lawn mowing work, it isnecessary to increase the rotation number of the left blade 91L with theincrease in the speed VBL.

On the other hand, as the speed VBL reduces, an area where the leftblade 91L performs lawn mowing work per unit time decreases. In thiscase, even when the rotation number of the left blade 91L is decreasedcompared to the rotation number when the speed VBL is greater, theaccuracy of the lawn mowing work is not lowered. Therefore, the rotationnumber of the left blade 91L decreases with reduction in the speed VBL,so that it is possible to improve energy saving performance (reduceelectric power consumed by the left blade motor 92L).

Therefore, in the above rotation number map, in a case where the speedVBL of the left blade 91L is within a range from greater than VB1 to notgreater than VB2 (VB1<VBL≦VB2), the target rotation number VML of theleft blade motor 92L is set so as to increase and decrease with increaseand reduction in the speed VBL of the left blade 91L. Consequently, itis possible to improve energy saving performance while suitablyperforming lawn mowing work.

In the rotation number map, in a case where the speed VBL of the leftblade 91L is greater than VB2 (VB2<VBL), the target rotation number VMLof the left blade motor 92L is set to VM2 (a value greater than VM1).The value VM2 of this target rotation number VML is set to the rotationnumber that is sufficiently high to enable accurate mowing work evenwhen the speed VBL of the left blade 91L is any value.

Thus, in a range in which VBL is small (0<VBL≦VB1), the target rotationnumber VML is constantly held to the minimum value VM1, so that theminimum rotation number of the left blade 91L necessary for performinglawn mowing work is secured. In a range in which VBL is large (VB2<VBL),the target rotation number VML is constantly held to the maximum valueVM2, so that the rotation number of the left blade 91L is prevented fromincreasing more than necessary.

The controller 24 a determines the target rotation number VML of theleft blade motor 92L based on the rotation number map set as describedabove, and the detected speed VBL of the left blade 91L.

In a case where the controller 24 a determines the target value of therotation number of the right blade 91R, namely the target rotationnumber VMR of the right blade motor 92R, the controller 24 a determinesthe target rotation number VMR based on the previously stored rotationnumber map (see FIG. 13), and the speed VBR of the right blade 91R tothe ground, which is detected in step S102.

The controller 24 a advances to step S104 after performing the processin step S103.

In step S104, the controller 24 a determines whether or not the targetrotation number VML of the left blade motor 92L, which is determined instep S103 is smaller than the current actual rotation number VMLa of theleft blade motor 92L.

In a case where the controller 24 a determines that the target rotationnumber VML of the left blade motor 92L is smaller than the currentactual rotation number VMLa of the left blade motor 92L, the controller24 a advances to step S105.

In a case where the controller 24 a determines that the target rotationnumber VML of the left blade motor 92L is not less than the currentactual rotation number VMLa of the left blade motor 92L, the controller24 a advances to step S106.

In step S104, the controller 24 a also determines whether or not thetarget rotation number VMR of the right blade motor 92R is smaller thanthe current actual rotation number VMRa of the right blade motor 92R.

In step S105, the controller 24 a determines whether or not the electricpower consumption PL of the left blade motor 92L is greater than apredetermined threshold value PLS. Specifically, the controller 24 adetermines based on a previously stored electric power consumptionthreshold map (see FIG. 14), the current actual rotation number VMLa ofthe left blade motor 92L, and the detected electric power consumption PLof the left blade motor 92L whether or not the electric powerconsumption PL of the left blade motor 92L is greater than thepredetermined threshold value PLS.

The electric power consumption of the blade motor 92 increases anddecreases in proportion to workloads applied to the blades 91 connectedto the blade motors 92. Therefore, the detection of the electric powerconsumption of the blade motors 92 by the controller 24 a means thedetection of workloads applied to the blades 91.

Herein, the electric power consumption threshold map is described withreference to FIG. 14.

In the electric power consumption threshold map, a threshold value PLSfor the electric power consumption PL of the left blade motor 92L, and athreshold value PRS for the electric power consumption PR of the rightblade motor 92R are set. The threshold value PLS and the threshold valuePRS are set to values greater than electric power consumption (electricpower shown by broken lines in FIG. 14) during the rotation of the blademotors 92 in a no-load state (state where the blades 91 are idledwithout performing lawn mowing work) by a predetermined ratio (or apredetermined value). Therefore, for example, in a case where theelectric power consumption PL of the left blade motor 92L is greaterthan the threshold value PLS (is included in the region T of FIG. 14),it can be determined that the left blade 91L is in the course of lawnmowing work, and a high load is applied to the left blade motor 92L.

The threshold value PLS and the threshold value PRS are the same valuein this embodiment, but can be set to respective different values.

The controller 24 a determines by using the electric power consumptionthreshold map set as described above whether or not the electric powerconsumption PL of the left blade motor 92L is greater than the thresholdvalue PLS for the current actual rotation number VMLa of the currentleft blade motor 92L (whether or not the electric power consumption PLis included in the region T of FIG. 14).

In a case where the controller 24 a determines that the electric powerconsumption PL is greater than the threshold value PLS, the controller24 a advances to step S101 again.

In a case where the controller 24 a determines that the electric powerconsumption PL is not greater than the threshold value PLS, thecontroller 24 a advances to step S106.

In step S105, the controller 24 a also determines whether or not theelectric power consumption PR of the right blade motor 92R is greaterthan the threshold value PRS for the current actual rotation number VMRaof the right blade motor 92R.

In step S106 shown in FIG. 12, the controller 24 a controls theoperation of the left blade motor 92L such that the left blade motor 92Lrotates at the target rotation number VML determined in step S103.

Similarly, the controller 24 a controls the operation of the right blademotor 92R such that the right blade motor 92R rotates at the targetrotation number VMR.

The controller 24 a advances to step S101 again after performing theprocess in step S106.

The controller 24 a performs the above energy-saving control (see FIG.12), so that it is possible to improve energy saving performance. Thatis, the controller 24 a increases and decreases the actual rotationnumber VMLa of the left blade motor 92L and the actual rotation numberVMRa of the right blade motor 92R in accordance with increase andreduction in the speed VBL of the left blade 91L and the speed VBR ofthe right blade 91R, thereby enabling improvement in energy saving.

For example, as shown in FIG. 15, in a case where the speed V of thelawn mower 1 (traveling machine body 10) is reduced (decelerated) whenthe lawn mower 1 performs lawn mowing work while reciprocating from oneend to the other end of a region L, for which lawn mowing work isperformed (a part shown by the broken line arrow A in FIG. 15), thespeed VBL of the left blade 91L and the speed VBR of the right blade 91Rare reduced. In this case, the controller 24 a decreases the actualrotation number VMLa of the left blade motor 92L and the actual rotationnumber VMRa of the right blade motor 92R to achieve energy saving.

Additionally, in a case where the lawn mower 1 turns (parts shown by thebroken line arrows B in FIG. 15), the lawn mower 1 is generallydecelerated, and therefore the speed VBL of the left blade 91L and thespeed VBR of the right blade 91R are reduced. Also in this case, thecontroller 24 a decreases the actual rotation number VMLa of the leftblade motor 92L and the actual rotation number VMRa of the right blademotor 92R to achieve energy saving.

Furthermore, in a case where the lawn mower 1 turns, the speed of theblade 91 located on the inner side is smaller than the speed of theblade 91 located on the outer side due to a difference between theturning radii. For example, in a case where the lawn mower 1 turns rightas shown in FIG. 16, a distance (turning radius) R1 from the turningcenter C of the lawn mower 1 (traveling machine body 10) to the centerof the right blade 91R is smaller than a distance (turning radius) R2from the turning center C to the center of the left blade 91L.Therefore, the speed VBR of the right blade 91R is smaller than thespeed VBL of the left blade 91L.

The controller 24 a individually decreases the actual rotation numberVMLa of the left blade motor 92L and the actual rotation number VMRa ofthe right blade motor 92R based on the speed VBL of the left blade 91Land the speed VBR of the right blade 91R, respectively. Therefore, theactual rotation number of the inner blade motor 92 (right blade motor92R in FIG. 16) can be made smaller than the actual rotation number ofthe outer blade motor 92 (left blade motor 92L in FIG. 16). Thus, theactual rotation numbers of the blade motors 92 are individuallycontrolled in accordance with the respective speeds of the blades 91, sothat it is possible to more effectively achieve energy saving.

Thus, the controller 24 a performs energy-saving control, so that it ispossible to reduce electric power consumed by the blade motors 92.Accompanying this, it is possible to achieve extension of moving time ofthe lawn mower 1, and reduction in size and cost with reduction in theloadage of the battery 21. In particular, the lawn mower 1 forperforming lawn mowing work often performs work while reciprocating, andtherefore have many opportunities of deceleration for checking thesurroundings, or turning, and a large energy saving effect by theenergy-saving control can be expected. Additionally, it is possible toreduce noise with reduction in the rotation numbers of the blade motors92 in the energy-saving control.

Even in a case where the speeds of the blades 91 are reduced, when theelectric power consumption of the blade motors 92 is greater than apredetermined threshold value, the controller 24 a determines that highloads are applied to the blades 91 (lawn mowing work is beingperformed), and does not perform control of decreasing the rotationnumbers of the blade motors 92. Consequently, even during theenergy-saving control, in a case where workloads are high, the rotationnumbers of the blade motors 92 are prevented from decreasing, and activelawn mowing work is performed, so that it is possible to preventdeterioration in the accuracy of the lawn mowing work (such asoccurrence of grass which is left long).

The vehicle body configuration of the lawn mower 1 shown in thisembodiment is an example, and the disclosure is not limited to the lawnmower 1.

For example, the lawn mower 1 may be configured such that the left motor22L and the right motor 22R are used as power sources for driving thepair of left and right driving wheels (the driving wheel 30L and thedriving wheel 30R), but may be configured such that other power source(such as an engine) is used. Additionally, the lawn mower 1 may beconfigured such that the respective motors (the left motor 22L, theright motor 22R, and the blade motors 92) are driven by using electricpower generated by the power of an engine.

Although the lawn mower 1 has the pair of left and right driving wheels,but the number of driving wheels, or the number of other wheels is notlimited. For example, the lawn mower 1 may be capable of four-wheeldrive like a work vehicle such as a general tractor.

Although the lawn mower 1 is driven based on the weight shift of aworker riding on the riding part 40, and the swing operation of thehandle 70 by the worker, the lawn mower may be driven by other drivingmethod (such as a driving method using a pedal for increasing andreducing the speed of the lawn mower 1).

Although the mower unit 90 is provided in the front part of thetraveling machine body 10, the configuration of the mower unit 90 is notlimited to this. The mower unit 90 can be provided on the back part orthe lower part of the traveling machine body 10.

In this embodiment, the blade motors 92 (working motors) using electricpower are used as power devices according to the disclosure. However,the disclosure is not limited to this. For example, transmissions (suchas a HST (hydrostatic continuously variable transmission)) provided tocorrespond to an engine and the respective blades 91 and capable ofproperly changing the power of the engine and transmitting the changedpower to the blades 91 can be used.

In this embodiment, the power devices (blade motors 92) are provided inthe mower unit 90. However, the disclosure is not limited to this. Forexample, power devices are provided in the traveling machine body 10,and rotational power from the power devices can be properly transmittedto the blades 91 of the mower unit 90.

In this embodiment, the two blades 91 are provided. However, thedisclosure is not limited to this, and the number of the blades 91 isnot limited.

In this embodiment, the controller 24 a detects the speeds of the blades91 based on the speed V and the angular speed ω of the traveling machinebody 10 to the ground. However, the disclosure is not limited to this.For example, the speeds of the blades 91 can be detected by usingvarious sensors (such as a ground speed sensor).

In this embodiment, the controller 24 a detects the speed V and theangular speed ω of the traveling machine body 10 based on the pair ofleft and right driving wheels. However, the disclosure is not limited tothis. For example, the speed V and the angular speed co can be detectedby using various sensors (such as a ground speed sensor and a gyrosensor).

The rotation number map (see FIG. 13) and the electric power consumptionthreshold map (see FIG. 14) exemplified in this embodiment are examples,and the contents thereof can be optionally set. For example, FIGS. 17Ato 17C each show another example of setting a rotation number map. FIG.17A shows an example of setting such that the target rotation number VMLincreases and decreases within a range of 0<VBL≦VB2 with increase andreduction in the speed VBL of the left blade 91L. FIG. 17B shows anexample of setting such that the target rotation number VML increasesand decreases within a range of VB1<VBL with increase and reduction inthe speed VBL of the left blade 91L. FIG. 17C shows an example ofsetting such that the target rotation number VML increases and decreaseswithin a range of 0<VBL with increase and reduction in the speed VBL ofthe left blade 91L.

The values of the target rotation numbers of the blade motors 92 (thetarget rotation number VML and the target rotation number VMR) in therotation number map are desirably set to appropriate values inaccordance with the diameters of the blades 91.

The lawn mower 1 may be provided with a notification unit (such as aliquid crystal monitor and a buzzer) for notifying a worker of acurrently selected control among the non-energy-saving control and theenergy-saving control.

1. A lawn mower comprising: a work device having a plurality of bladesfor performing lawn mowing work, the plurality of blades being driven byrotational power supplied by separate blade motors; a blade speeddetection unit configured to detect respective speeds of the pluralityof blades relative to a ground; and a control device configured toperform energy-saving control, wherein, during the energy-savingcontrol, the separate blade motors are controlled individually so thatthe plurality of blades rotate at different speeds and achieve reducedpower consumption during turning movement of the lawn mower.
 2. The lawnmower as claimed in claim 1, wherein the control device does notdecrease the rotation number of the rotational power transmitted to eachof the blades, in a case where a workload applied to each of the bladesis higher than a predetermined threshold value during the energy-savingcontrol.
 3. The lawn mower as claimed in claim 2, wherein the controldevice is capable of implementing non-energy-saving control ofcontrolling the rotation number of the rotational power transmitted toeach of the blades at a constant rotation number regardless of thespeeds of the plurality of blades relative to the ground.
 4. The lawnmower as claimed in claim 1, wherein the control device is capable ofimplementing non-energy-saving control of controlling the rotationnumber of the rotational power transmitted to each of the blades at aconstant rotation number regardless of the speeds of the plurality ofblades relative to the ground.
 5. The lawn mower as claimed in claim 4,further comprising a selection unit configured to select any one of theenergy-saving control and the non-energy-saving control to enable thecontrol device to implement the selected control.
 6. The lawn mower asclaimed in claim 1, wherein the control device does not decrease therotation number of the rotational power transmitted to each of theblades, in a case where a workload applied to each of the blades ishigher than a predetermined threshold value during the energy-savingcontrol.
 7. The lawn mower as claimed in claim 6, wherein the controldevice is capable of performing non-energy-saving control of controllingthe rotation number of the rotational power transmitted to each of theblades at a constant rotation number regardless of the speeds of theplurality of blades relative to the ground.
 8. The lawn mower as claimedin claim 1, wherein the control device is capable of performingnon-energy-saving control of controlling the rotation number of therotational power transmitted to each of the blades at a constantrotation number regardless of the speeds of the plurality of bladesrelative to the ground.
 9. A lawn mower comprising: a traveling vehiclebody; a mower unit coupled to the traveling vehicle body and comprisingblade motors; each blade motor rotating a blade for performing lawnmowing work; a blade speed detection unit; and a control deviceperforming an energy-saving control during turning movement of the lawnmower, wherein, during the energy-saving control, the blade motorsoperate with different rotation speeds and power consumption.